It is commonly known in the field of gas turbine engines to bleed cooling air derived from the compressor between components subjected to high circumferential and/or thermal forces in operation so as to purge hot gaspath air from the leakage path and to moderate the temperature of the adjacent components. The cooling air passes through the leakage path and is introduced into the main working fluid flowpath of the engine. Such is the case where the leakage path is between a stator and a rotor assembly. In fact, at high rotational speed, the rotor assembly propels the leakage air flow centrifugally much as an impeller.
Such air leakage into the working fluid flowpath of the engine is known to have a significant impact on turbine efficiency. Accordingly, there is a need for controlling leakage air into the working fluid flowpath of gas turbine engines.